Effects Of Bilirubin On The Functions Of Cord Blood T-Lymphocytes

Objective To study the effects of bilirubin on the functions of cord blood T-lymphocytes.Methods 21 full-term neonates were involved in this study. Cord blood mononuclear cells (CBMC) were in vitro preincubated with unconjugated bilirubin dissolved in bovine albumin solution at various levels (0-12mg/dl), washed, and further cultured with PHA for 48 hours. The apoptosis index of lymphocytes of CBMC after cultivation was determined by AB/EO dying methods. The positive expression rate of CD₂₅ (IL-2 receptor) was detected by indirect immuno- fluorescence procedure. The levels of IFN-γ and IL-4 in the supernatants of CBMC were detected by ELISA.Results (1) The apoptosis index (AI) of the 0mg/dl group , 6mg/dl group, 9mg/dl group and 12mg/dl group was (28.72±11.09)%, (32.44±12.72)%, (56.36±9.24)%, (61.49±8.93)% , respectively. By comparison, the AI of the 12mg/dl group was significantly higher than that of the 6mg/dl group and Omg/dl group (q= 12.55,14.16, p<0.01), and the AI of the 9mg/dl group was obviously higher than that of the 6mg/dl and 0mg/dl group (q=10.34, 11.94, p<0.01). But there was no difference between the AI of the 12mg/dl group and that of the 9mg/dl group (q=2.22, p>0.05), meanwhile no difference of the AI was found between the 6mg/dl group and the 0mg/dl group (q=1.60, p>0.05). (2) The positive expression rates of CD25 of the 0mg/dl group, 6mg/dl group, 9mg/dl group and 12mg/dl group were (64.25±6.18)%, (67.28±4.87)%, (22.12±4.61)% and (19.89±6.72)%, respectively. By comparison, the positive expression rate of CD₂₅ of the 12mg/dl group was remarkably lower than that of the 6mg/dl and 0mg/dl group (q=38.35, 35.90, p<0.01),and the positive expression rate of CD₂₅ of the 9mg/dl group was apparently lower than that of the 6mg/dl and Omg/dl group (q=36.54, 34.09, p<0.01). But there was no difference between the positive expressions rate of CD₂₅ of the 12mg/dl group and that of the 9mg/dl group (q=1.81, p>0.05), meanwhile no difference of the positive expression rate of CD25 was found between the 6mg/dl group and the 0mg/dl group (q=2.45, p>0.05). (3) After the treatment with bilirubin of various concentration, the levels of IFN-γ of the 12mg/dl group produced by CBMC were significantly lower than that of the 6mg/dl and 0mg/dl group (q=38.17, 41.95, p<0.01). the IFN-γ levels of the 9mg/dl group were remarkably lower than that of the 6mg/dl and 0mg/dl group (q=35.95, 39.73, p<0.01), and that of the 6mg/dl group were lower than that of the 0mg/dl group (q=3.78, p<0.05). There was no difference of the IFN-γ levels between the 12mg/dl group and the 9mg/dl group (q=2.21, p>0.05). (D No significant difference of IL-4 levels in supernatants of CBMC was found among the four groups (p>0.05). (5) The ratio of IFN-γ/IL-4 of the 12mg/dl group was much lower than that of the 6mg/dl group and Omg/dl group (q=13.28 , 16.23, p<0.01). The ratio of IFN-γ/IL-4 of the 9mg/dl group was markedly lower than that of the 6mg/dl and 0mg/dl group (q=12.49, 15.44,...